Synthesis of Tuber mesentericum ectomycorrhizae with Quercus pubescens: a morphological review and DNA characterization

Tuber mesentericum Vittad., also known as the “black truffle of Bagnoli Irpino”, is a lesser known ectomycorrhizal hypogeous fungus in the Pezizales. Known from the majority of European countries, this species characteristically lives in loose, easily warming up, calcareous soils. The aim of this study was to propose a comprehensive morphological description of T. mesentericum ectomycorrhiza (ECM) supported by photographs and molecular data. Previous data suggested that T. mesentericum ECM have high similarity to those of T. aestivum Vittad. However, the high variability of the ITS region of the nuclear ribosomal DNA in T. mesentericum makes it impossible to design primers able to selectively amplify all the genotypes of this species. Mycorrhization percentages on 16 Quercus pubescens Willd. seedlings inoculated with T. mesentericum, were assessed over a period of 9 (first time-point) and 14 (second time-point) months. Two different quantities of the spore-slurry were used to inoculate two batches of plants (batches A and B). At the first time-point the presence of non-target ECM contaminant Pulvinula constellatio (Berk. & Broome) Boud. was detected with an average level of root colonization of 15 %. After 14 months T. mesentericum produced wellformed ECM with a rate of 20 % and 40 % in batches A and B, respectively. ITS region from ECM and ascomata used for the inoculum were sequenced and compared with T. aestivum and T. mesentericum sequences available in GenBank.